1 files changed, 90 insertions, 0 deletions
diff --git a/examples/struct-log-self.rs b/examples/struct-log-self.rs
new file mode 100644
index 0000000..f533766
--- /dev/null
+++ b/examples/struct-log-self.rs
@@ -0,0 +1,90 @@
+//! Example of how to implement `KV` for a struct
+//! to conveniently log data associated with it.
+#[macro_use]
+extern crate slog;
+use slog::*;
+
+mod common;
+
+struct Peer {
+    host: String,
+    port: u32,
+}
+
+impl Peer {
+    fn new(host: String, port: u32) -> Self {
+        Peer {
+            host: host,
+            port: port,
+        }
+    }
+}
+
+// `KV` can be implemented for a struct
+impl KV for Peer {
+    fn serialize(&self, _record: &Record, serializer: &mut Serializer) -> Result {
+        serializer.emit_u32(Key::from("peer-port"), self.port)?;
+        serializer.emit_str(Key::from("peer-host"), &self.host)?;
+        Ok(())
+    }
+}
+
+struct Server {
+    _host: String,
+    _port: u32,
+    // One approach is to create new `Logger` with struct data
+    // and embedded it into struct itself.  This works when struct is mostly
+    // immutable.
+    log: Logger,
+}
+
+impl Server {
+    fn new(host: String, port: u32, log: Logger) -> Server {
+        let log = log.new(o!("server-host" => host.clone(), "server-port" => port));
+        Server {
+            _host: host,
+            _port: port,
+            log: log,
+        }
+    }
+
+    fn connection(&self, peer: &Peer) {
+        // Another approach is to add struct to a logging message when it's
+        // necessary. This might be necessary when struct data can change
+        // between different logging statements (not the case here for `Peer`).
+        info!(self.log, "new connection"; peer);
+    }
+}
+
+struct PeerCounter {
+    count: usize,
+    log: Logger,
+}
+
+impl PeerCounter {
+    fn new(log: Logger) -> Self {
+        PeerCounter { count: 0, log: log }
+    }
+
+    // A hybrid approach with `Logger` with parent logging-context embedded into
+    // a `struct` and a helper function adding mutable fields.
+    fn log_info(&self, msg: &str, kv: BorrowedKV) {
+        info!(self.log, "{}", msg; "current-count" => self.count, kv);
+    }
+
+    fn count(&mut self, peer: &Peer) {
+        self.count += 1;
+        self.log_info("counted peer", b!(peer));
+    }
+}
+
+fn main() {
+    let log = Logger::root(Fuse(common::PrintlnDrain), o!("build-id" => "7.3.3-abcdef"));
+
+    let server = Server::new("localhost".into(), 12345, log.clone());
+
+    let peer = Peer::new("1.2.3.4".into(), 999);
+    server.connection(&peer);
+    let mut counter = PeerCounter::new(log);
+    counter.count(&peer);
+}